Religion is a large and diverse category of social institutions and activities. It encompasses a wide variety of beliefs and practices, from those of Abrahamic faiths to those of Wiccans, satanists, or pagans. The concept has a complex and dynamic history, and as with other concepts in social science, definitions of Religion are often subject to revision. Unlike some other social institutions, which can change rapidly over time and across cultures, religious beliefs and practices are more viscous, and tend to adapt slowly or retain certain features over long periods.

A number of different approaches to the study of Religion have been developed. Most have been “monothetic,” operating under the classical view that a concept can be accurately defined only when all instances share a particular defining property. In contrast, recent decades have seen the development of “polythetic” approaches to the study of Religion.

Polythetic definitions of Religion seek to classify it by looking for a combination of properties. For example, James G. Frazer’s famous statement that a religion is a belief in powers greater than man and an attempt to propitiate or please them (Frazer 1922) exemplifies a polythetic approach.

Other definitions of Religion concentrate on activities and behaviors. These often emphasize the use of rituals, prayers, or confessions of doctrinal beliefs. They also include the social organization of a religion, including its leaders and followers. It is important to recognize that this approach shifts attention away from hidden mental states, and toward visible institutional structures. However, some scholars of Religion argue that this is a mistake and that researchers should refocus their attention on mental states in their analysis of Religion.